(1) Background of the Invention
The present invention relates to diagnosis apparatus and method for diagnosing a connection state of a vehicle antenna, the vehicle antenna performing transmission and reception of electric waves between an in-board unit mounted in the vehicle and a portable unit for the vehicle.
(2) Description of Related Art
A system has been proposed which performs unlock and lock of a vehicular door lock mechanism and start and stop of an engine by communicating between the in-board unit and the portable unit and by performing an ID collation therebetween via the antenna. In the previously proposed system described above, an external exclusively used (or a dedicated) diagnosis device is connected to the system to determine whether the connection state of the in-board unit mounted in the vehicle to the vehicle antenna is normal (refer to a Japanese service manual for Nissan FUGA (document code: SM4J1Y50J0 published in October of 2004).